Methods and systems for representing errors

ABSTRACT

Disclosed are systems, devices and methods for transmission of messages between wireless transceiver devices including fields representing values such as, for example, a range between devices, time of transmission of a message or time of receipt of a previous message. In particular embodiments, message may also comprise fields to express a maximum error in values representing range, time of transmission of a message or time of receipt of a previous message.

This application claims the benefit of U.S. Provisional Application No.62/233,940, entitled “Methods and Systems for Representing Errors,”filed Sep. 28, 2015, which is assigned to the assignee thereof and whichis expressly incorporated herein by reference.

BACKGROUND

Field

Embodiments described herein are directed to obtaining measurements ofsignals acquired from a mobile transmitter.

Information

Satellite positioning systems (SPSs), such as the global positioningsystem (GPS), have enabled navigation services for mobile handsets inoutdoor environments. Likewise, particular techniques for obtainingestimates of positions of mobile device in indoor environments mayenable enhanced location based services in particular indoor venues suchas residential, governmental or commercial venues. For example, a rangebetween a mobile device and a transceiver positioned at fixed locationmay be measured based, at least in part, on a measurement of a roundtrip time (RTT) measured between transmission of a first message from afirst device to a second device and receipt of a second message at thefirst device transmitted in response to the first message.

SUMMARY

Briefly, one particular implementation is directed to a method, at afirst wireless station (STA) comprising: transmitting a fine timingmeasurement (FTM) message comprising at least a time of departure (TOD)field and at least one other field, the at least one other fieldexpressing a maximum TOD error in five bits or less, the at least oneother field being capable of expressing the maximum TOD error as largeas 1.0 msec.

Another particular implementation is directed to a first wirelessstation (STA), comprising: a wireless transceiver to transmit messagesto and receive messages from a wireless communication network; and oneor more processors coupled to the wireless transmitter, the one or moreprocessors being configured to: initiate transmission of a fine timingmeasurement (FTM) message through the wireless transceiver comprising atleast a time of departure (TOD) field and at least one other field, theat least one other field expressing a maximum TOD error in five bits orless, the at least one other field being capable of expressing themaximum TOD error as large as 1.0 msec.

Another particular implementation is directed to a first wirelessstation (STA), comprising: means for receiving a fine timing measurement(FTM) request message; and means for transmitting an FTM message inresponse to the FTM request message comprising at least a time ofdeparture (TOD) field and at least one other field, the at least oneother field expressing a maximum TOD error in five bits or less, the atleast one other field being capable of expressing the maximum TOD erroras large as 1.0 msec.

Another particular implementation is directed to a non-transitorystorage medium having computer-readable instructions stored thereonwhich are executable by a process of a first wireless station (STA) to:initiate transmission of a fine timing measurement (FTM) message througha wireless transmitter comprising at least a time of departure (TOD)field and at least one other field, the at least one other fieldexpressing a maximum TOD error in five bits or less, the at least oneother field being capable of expressing the maximum TOD error as largeas 1.0 msec.

One particular embodiment is directed to a method, at a first wirelessstation, comprising: transmitting a fine timing measurement (FTM) rangereport message comprising at least a range field and at least one otherfield, the at least one other field being capable of expressing amaximum range error in five bits or less of up to at least 2000 m. Inone particular implementation, the at least one other field expressesthe maximum range error as an exponent. In another particularimplementation, the at least one other field is further capable ofexpressing the maximum range error at least as small as 0.00025 m.

Another particular embodiment is directed to a non-transitory storagemedium having computer-readable instructions stored thereon which areexecutable by a process of a first wireless station (STA) to: initiatetransmission of a fine timing measurement (FTM) message through awireless transmitter comprising at least a range field and at least oneother field, the at least on other field being capable of expressing amaximum range error in five bits or less of up to at least 2000 m. Inone particular implementation, the at least one other field expressesthe maximum range error as an exponent. In another particularimplementation, the at least one other field is further capable ofexpressing the maximum range error at least as small as 0.00025 m.

Another particular embodiment is directed to a first wireless station(STA), comprising: a wireless transceiver to transmit messages to awireless communication network; and one or more processors coupled tothe wireless transmitter, the one or more processors being configuredto: initiate transmission of a fine timing measurement (FTM) messagethrough the wireless transmitter comprising at least a range field andat least one other field, the at least one other field being capable ofexpressing a maximum range error in five bits or less of up to at least2000 m. In one particular implementation, the at least one other fieldexpresses the maximum range error as an exponent. In another particularimplementation, the at least one other field is further capable ofexpressing the maximum range error at least as small as 0.00025 m.

Another particular embodiment is directed to a first wireless station,comprising: means for receiving one or more fine timing measurement(FTM) messages; and means for transmitting an FTM range report messagebased, at least in part, on the received one or more FTM messages, theFTM range report message comprising at least a range field and at leastone other field, the at least one other field being capable ofexpressing a maximum range error in five bits or less of up to at least2000 m. In one particular implementation, the at least one other fieldexpresses the maximum range error as an exponent. In another particularimplementation, the at least one other field is further capable ofexpressing the maximum range error at least as small as 0.00025 m.

Another particular embodiment is directed to a first wireless station(STA), comprising: receiving a fine timing measurement (FTM) messagecomprising at least a time of departure (TOD) field and at least oneother field, the at least one other field expressing a maximum TOD errorin five bits or less; and decoding the at least one other field todetermine the maximum TOD error as large as 1.0 msec. In one particularimplementation, the FTM message is transmitted by a second STA inresponse to receipt of a FTM request message transmitted by the firstSTA. In another particular implementation, the at least one other fieldexpresses the maximum TOD error as an exponent. In another particularimplementation, the FTM message further comprises a time of arrival(TOA) field and at least one other field expressing a maximum TOA errorin five bits or less, method further comprising decoding the at leastone other field to determine the maximum TOA error as large as 1.0 msec.In another particular implementation, the at least one other field beingcapable of expressing the maximum TOA error as small as 1.0 psec. Inanother particular implementation, the at least one other field isfurther capable of expressing the maximum TOD error as small as 1.0psec.

Another particular implementation is directed to a first wirelessstation (STA), comprising: a wireless transceiver to receive messagesfrom a wireless communication network; and one or more processorsconfigured to: obtain a fine timing measurement (FTM) message receivedat the wireless receiver comprising at least a time of departure (TOD)field and at least one other field, the at least one other fieldexpressing a maximum TOD error in five bits or less; and decode the atleast one other field to determine the maximum TOD error as large as 1.0msec. In one particular implementation, the FTM message is transmittedby a second STA in response to receipt of a FTM request messagetransmitted by the first STA. In another particular implementation, theat least one other field expresses the maximum TOD error as an exponent.In another particular implementation, the FTM message further comprisesa time of arrival (TOA) field and at least one other field expressing amaximum TOA error in five bits or less, and wherein the one or moreprocessors are further configured to decode the at least one other fieldto determine the maximum TOA error as large as 1.0 msec. In anotherparticular implementation, the at least one other field being capable ofexpressing the maximum TOA error as small as 1.0 psec. In anotherparticular implementation, the at least one other field is furthercapable of expressing the maximum TOD error as small as 1.0 psec.

In another particular embodiment, a first wireless station (STA),comprising: means for receiving a fine timing measurement (FTM) messagecomprising at least a time of departure (TOD) field and at least oneother field, the at least one other field expressing a maximum TOD errorin five bits or less; and means for decoding the at least one otherfield to determine the maximum TOD error as large as 1.0 msec. In oneparticular implementation, the FTM message is transmitted by a secondSTA in response to receipt of a FTM request message transmitted by thefirst STA. In another particular implementation, the at least one otherfield expresses the maximum TOD error as an exponent. In anotherparticular implementation, the FTM message further comprises a time ofarrival (TOA) field and at least one other field expressing a maximumTOA error in five bits or less, the first STA further comprising meansfor decoding the at least one other field to determine the maximum TOAerror as large as 1.0 msec. In another particular implementation, the atleast one other field being capable of expressing the maximum TOA erroras small as 1.0 psec. In another particular implementation, the at leastone other field is further capable of expressing the maximum TOD erroras small as 1.0 psec.

Another particular implementation is directed to a non-transitorystorage medium having computer-readable instructions stored thereonwhich are executable by a processor of a first wireless station (STA)to: obtain a fine timing measurement (FTM) message received at awireless transmitter comprising at least a time of departure (TOD) fieldand at least one other field, the at least one other field expressing amaximum TOD error in five bits or less; and decode the at least oneother field to determine the maximum TOD error as large as 1.0 msec. Inone particular implementation, the FTM message is transmitted by asecond STA in response to receipt of a FTM request message transmittedby the first STA. In another particular implementation, the at least oneother field expresses the maximum TOD error as an exponent. In anotherparticular implementation, the FTM message further comprises a time ofarrival (TOA) field and at least one other field expressing a maximumTOA error in five bits or less, and wherein the instructions are furtherexecutable by the processor to decode the at least one other field todetermine the maximum TOA error as large as 1.0 msec. In anotherparticular implementation, the at least one other field being capable ofexpressing the maximum TOA error as small as 1.0 psec. In anotherparticular implementation, the at least one other field is furthercapable of expressing the maximum TOD error as small as 1.0 psec.

Another particular embodiment is directed to a method, at a firstwireless station, comprising: receiving a fine timing measurement (FTM)range report message comprising at least a range field and at least oneother field, the at least one other field being capable of expressing amaximum range error in five bits or less; and decoding the at least oneother field to determine the maximum range error up to at least 2000 m.

In another particular embodiment is directed to a non-transitory storagemedium having computer-readable instructions stored thereon which areexecutable by a process of a first wireless station (STA) to: obtain afine timing measurement (FTM) message received at a wireless receivercomprising at least a range field and at least one other field, the atleast one other field being capable of expressing a maximum range errorin five bits or less; and decode the at least one other field todetermine the maximum range error up to at least 2000 m.

Another particular embodiment is directed to a first wireless station(STA), comprising: a wireless receiver to receive messages from awireless communication network; and one or more processors coupled tothe wireless receiver, the one or more processors being configured to:obtain a fine timing measurement (FTM) message received at the wirelessreceiver comprising at least a range field and at least one other field,the at least one other field being capable of expressing a maximum rangeerror in five bits or less; and decode the at least one other field todetermine the maximum range error up to at least 2000 m.

Another particular embodiment is directed to a first wireless station,comprising: means for receiving a fine timing measurement (FTM) rangereport message comprising at least a range field and at least one otherfield, the at least one other field being capable of expressing amaximum range error in five bits or less; and means for decoding the atleast one other field to determine the maximum range error up to atleast 2000 m.

It should be understood that the aforementioned implementations aremerely example implementations, and that claimed subject matter is notnecessarily limited to any particular aspect of these exampleimplementations.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive aspects are described with reference tothe following figures, wherein like reference numerals refer to likeparts throughout the various figures unless otherwise specified.

FIG. 1 is a system diagram illustrating certain features of a systemcontaining a mobile device, in accordance with an implementation.

FIG. 2 is a diagram illustrating a message flow between wirelessstations (STAs) according to particular embodiments.

FIGS. 3 and 4 are flow diagrams of processes to exchange fine timingmeasurement (FTM) messages according to a particular embodiment.

FIG. 5 shows fields of a fine timing measurement (FTM) request messageaccording to a particular embodiment.

FIG. 6 is a flow diagram illustrating a message flow between wirelessstations (STAs) according to particular embodiments.

FIGS. 7 and 8 are flow diagrams of processes to exchange FTM rangereport messages according to a particular embodiment.

FIG. 9 shows fields of an FTM range report message according to aparticular embodiment.

FIG. 10 is a schematic block diagram illustrating an exemplary device,in accordance with an implementation.

FIG. 11 is a schematic block diagram of an example computing system inaccordance with an implementation.

DETAILED DESCRIPTION

As discussed below, particular message flows may enable effective andefficient measurements of a round trip time (RTT) or time of flight(TOF) in connection with a transmission of messages between wirelessstations (STAs). In a particular example, a STA may comprise any one ofseveral types of transceiver devices such as, for example, a mobile userstation (e.g., smartphone, notebook computer, wireless audio speakerdevice, tablet computer, etc.) or wireless service access device (e.g.,wireless local area network (WLAN) access point, personal area network(PAN) or femto cell). Particular message flows and fields in messageframes may enable obtaining RTT of TOF measurements with sufficientaccuracy for measuring a range between the wireless STAs, for example.Such a measured range may be used in any one of several applicationsincluding positioning operations, for example.

In some implementations, different STAs may maintain synchronized clockstates to assist with coordinating actions between different STAs inparticular applications. According to an embodiment, a first STA andsecond STA may exchange messages to, among other things, synchronizeclock states maintained at the first and second STAs. The first STA maysynchronize the clock state maintained at the first STA with the clockstate maintained at the second STA based, at least in part, on precisionvalues in messages received at the first STA indicating a time oftransmission of the messages or times of receipt of previous messages.Synchronizing the first clock with the second clock, the first wirelesstransceiver device may enable coordinated operations between the firstand second wireless transceiver devices to perform particular functionssuch as, for example, obtaining ranging measurements.

As discussed below, a first STA may transmit an FTM request message to asecond STA to initiate a process for an exchange of messages or framesenabling the second STA to synchronize a state of a clock to a state ofa clock maintained by another device. In this context, an “FTM requestmessage” comprises a message comprising one or more fields to expressvalues indicative of a time of transmission of the FTM message or a timeof receipt of a previous message, or a combination thereof. Inparticular implementations as discussed below, the first and second STAsmay synchronize respective clock states by exchanging messages toprecision values indicating times of transmission of the messages andtime of receipt of previous messages.

According to an embodiment, as shown in FIG. 1, mobiles device 100 a or100 b may transmit radio signals to, and receive radio signals from, awireless communication network. In one example, a mobile device 100 maycommunicate with a communication network by transmitting wirelesssignals to, or receiving wireless signals from, a local transceiver 115over a wireless communication link 125.

In a particular implementation, a local transceiver 115 may bepositioned in an indoor environment. A local transceiver 115 may provideaccess to a wireless local area network (WLAN, e.g., IEEE Std. 802.11network) or wireless personal area network (WPAN, e.g., Bluetoothnetwork). In another example implementation, a local transceiver 115 maycomprise a femto cell transceiver capable of facilitating communicationon wireless communication link 125 according to a cellular communicationprotocol. Of course it should be understood that these are merelyexamples of networks that may communicate with a mobile device over awireless link, and claimed subject matter is not limited in thisrespect.

In a particular implementation, local transceiver 115 a or 115 b maycommunicate with servers 140, 150 and/or 155 over a network 130 throughlinks 145. Here, network 130 may comprise any combination of wired orwireless links. In a particular implementation, network 130 may compriseInternet Protocol (IP) infrastructure capable of facilitatingcommunication between a mobile device 100 and servers 140, 150 or 155through a local transceiver 115. In another implementation, network 130may comprise wired or wireless communication network infrastructure tofacilitate mobile cellular communication with mobile device 100.

In a particular implementation, mobile device 100 may be capable ofcomputing a position fix based, at least in part, on signals acquiredfrom local transmitters (e.g., WLAN access points positioned at knownlocations). For example, mobile devices may obtain a position fix bymeasuring ranges to three or more indoor terrestrial wireless accesspoints which are positioned at known locations. Such ranges may bemeasured, for example, by obtaining a MAC ID address from signalsreceived from such access points and obtaining range measurements to theaccess points by measuring one or more characteristics of signalsreceived from such access points such as, for example, received signalstrength (RSSI) or RTT. In alternative implementations, mobile device100 may obtain an indoor position fix by applying characteristics ofacquired signals to a radio heatmap indicating expected angle of arrival(AoA). In other alternative implementations, as pointed out above,mobile device 100 may obtain an indoor position fix by applyingcharacteristics of acquired signals to a radio heatmap indicatingexpected TOF. Accordingly, a radio heatmap may comprising TOF, AoA, RSSIand/or RTT signatures at particular locations in an indoor area. Inparticular implementations, a radio heatmap may associate identities oflocal transmitters (e.g., a MAC address which is discernible from asignal acquired from a local transmitter), expected RSSI from signalstransmitted by the identified local transmitters, an expected RTT fromthe identified transmitters, and possibly standard deviations from theseexpected AoA, TOF, RSSI or RTT. It should be understood, however, thatthese are merely examples of values that may be stored in a radioheatmap, and that claimed subject matter is not limited in this respect.

In a particular implementation, a mobile device 100 or local transceiver115 may be capable of computing a position fix based, at least in part,on signals acquired from local transmitters (e.g., WLAN access pointspositioned at known locations). For example, a receiver device (e.g., amobile device 100 or local transceiver 115) may obtain a position fix bymeasuring ranges to three or more indoor terrestrial wireless accesspoints which are positioned at known locations. Such ranges may bemeasured, for example, by obtaining a MAC ID address from signalsreceived from such access points and obtaining range measurements to theaccess points by measuring one or more characteristics of signalsreceived from such access points such as, for example, received signalstrength (RSSI) or RTT. In alternative implementations, a mobile device100 may obtain an indoor position fix by applying characteristics ofacquired signals to a radio heatmap indicating expected RSSI and/or RTTsignatures at particular locations in an indoor area. In particularimplementations, a radio heatmap may associate identities of localtransmitters (e.g., a MAC address which is discernible from a signalacquired from a local transmitter), expected RSSI from signalstransmitted by the identified local transmitters, an expected RTT fromthe identified transmitters, and possibly standard deviations from theseexpected RSSI or RTT. It should be understood, however, that these aremerely examples of values that may be stored in a radio heatmap, andthat claimed subject matter is not limited in this respect.

In particular implementations, a mobile device 100 or a localtransceiver 115 may receive positioning assistance data for indoorpositioning operations from servers 140, 150 or 155. For example, suchpositioning assistance data may include locations and identities oftransmitters positioned at known locations to enable measuring ranges tothese transmitters based, at least in part, on a measured RSSI and/orRTT, for example. Other positioning assistance data to aid indoorpositioning operations may include radio heatmaps, magnetic heatmaps,locations and identities of transmitters, routeability graphs, just toname a few examples.

In a particular implementation, particular messages flows betweenwireless STAs may be implemented for obtaining a measurement of RTT froman exchange of messages between the STAs for use in positioningoperations as discussed above. In particular implementations, asdescribed below, any STA may comprise a mobile device (e.g., mobiledevice 100) or a stationary transceiver (e.g., IEEE std. 802.11 accesspoint, stationary Bluetooth device, local transceiver 115, etc.). Assuch, an exchange of messages between wireless STAs may comprise anexchange of messages between a mobile device and a stationarytransceiver (e.g., between a mobile device 100 and local transceiver 115over a wireless link 125), between two peer mobile devices (e.g.,between mobile devices 100 a and 100 b over wireless link 159), orbetween two stationary transceivers (e.g., between local transceiver 115a and local transceiver 115 b over wireless link 179), just to provide afew examples. In particular implementations, various techniquesdescribed herein may incorporate some, but not necessarily all, aspectsor features of IEEE P802.11-REVmc™/D4.2 Draft Standard 802.11 forInformation technology—Telecommunications and information exchangebetween systems, Local and metropolitan area networks—Specificrequirements Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY), September 2015, section 11.24.6 (hereinafter “IEEEP802.11-REVmc™/D5.3”). Indeed, it should be understood that somefeatures described herein are not shown, described or taught in IEEEP802.11-REVmc™/D5.3.

FIG. 2 is a diagram illustrating a message flow between wirelessstations (STAs) including a (first) “initiating” STA and a (second)“responding” STA according to an example embodiment. In this context, aresponding STA or initiating STA may comprise any one of severaltransceiver devices including a mobile device (e.g., mobile device 100)or stationary access transceiver device (e.g., local transceiver 115).It should be understood, however, that these are merely examples of aninitiating STA or a responding STA, and claimed subject matter is notlimited in this respect. An initiating STA may obtain or compute one ormore measurements of RTT based, at least in part, on timing of messagesor frames transmitted between the initiating STA and a responding STA.As used herein, the terms “message” and “frame” are usedinterchangeably. The initiating STA may transmit a TM or FTM requestmessage or frame (“Request”) 202 to the responding STA and receive anacknowledgement message or frame (“Ack”) 204 transmitted in response. Ina particular implementation, while not limiting claimed subject matterin this respect, contents of such an FTM request message may be as shownin the IEEE P802.11-REVmc™/D5.3. In particular implementations, such anAck frame 204 may provide an indication of receipt of a previouslytransmitted message. The initiating STA may then obtain or compute anRTT measurement based, at least in part, on time stamp values (t1, t4)provided in TM or FTM messages or frames (“M”) 206 received from theresponding STA (and transmitted in response to receipt of a fine timingmeasurement request message). In a particular implementation, as shownin the message flow diagram, a sequence of multiple exchanges ofalternating TM or FTM messages 206 followed by acknowledgement messages208 may create additional time stamp values (t1, t2, t3 and t4).

According to an embodiment, a TM or FTM request message transmitted byan initiating STA may include fields, parameters, etc. characterizing adesired exchange of messages with a responding STA to provide TM or FTMmeasurements to the initiating STA enabling the initiating STA tocompute a measurement (e.g., TOF or RTT). In response to receipt of a TMor FTM request message, a responding STA may transmit to the initiatingSTA one or more TM messages or FTM messages including measurements orparameters enabling the initiating STA to compute RTT, TOF or otherparameters indicative of range.

In a particular implementation, while not limiting claimed subjectmatter in this respect, contents of such an FTM message or frame may beas shown in the IEEE P802.11-REVmc™/D5.3. In one example implementation,an initiating STA may compute an RTT measurement as (t4−t1)−(t3−t2),where t2 and t3 are the time of receipt of a previous FTM message orframe and transmission of a preceding acknowledgement message or frame,respectively. Similarly, with exactly the same set of frames, theinitiating STA can compute a clock offset as ½*((t2−t1)−(t4−t3)). Theinitiating STA may transmit a single FTM request message to obtain acorresponding number of RTT measurements which may be combined forcancellation of unbiased measurement noise in computing a range oroffset between the receiving and responding STAs.

According to an embodiment, an FTM message (e.g., a message 206transmitted as an FTM message) may include a time of arrival (TOA) fieldindicating a time of receipt of an FTM request message and a time ofdeparture (TOD) field indicating a time that the FTM is beingtransmitted. The FTM message may express values in the TOA and TODfields according to a clock maintained at a responding STA. Here, theresponding STA may also determine a maximum error associated with valuesin the TOA and TOD fields, which may be expressed as an exponent,according to embodiments as discussed below.

As TOD and TOA values in FTM messages have transitioned from 100 ps to 1ps level accuracy, bit widths of the timestamp Error fields (e.g.,expressing maximum errors in TOA or TOD) were kept the same and themaximum error values were reduced from 3.2767 μs to 1.064896 μs. Whilethese maximum values may be appropriate for ranging operations, thisaccuracy may not be sufficient for synchronization of clock statesmaintained at a responding STA and an initiating STA, where an errorfield can be as large as 1.0 ms.

According to an embodiment, the number of bits to express a maximumerror in a TOA or TOD value may be reduced from fifteen bits to fivebits. FIGS. 3 and 4 illustrate aspects of processes that may beperformed at STAs for transmission and processing of an FTM messageaccording to particular embodiments. At block 302, a responding STA mayreceive an FTM request message (e.g., FTM request message 202)transmitted by an initiating STA. In response to the FTM requestmessage, at block 304 the responding STA may transmit an FTM messagecomprising a first field expressing a time of departure (e.g., TOD) ofthe FTM message and at least one other second field expressing a maximumerror in a value expressed in the first field. The second field mayexpress the maximum error in the value expressed first field as being aslarge as 1.0 msec and in five bits or less. In particularimplementations, actions set forth at blocks 302 and 304 may beperformed using any one of several structures such as, for example,wireless transceiver 1121 in combination with processing structures suchas general purpose/application processor 1111, DSP(s) 1112 and/or modemprocessor 1166 (e.g., executing instructions stored in memory 1140) asshown in FIG. 10, or communication interface 1830 in combination withprocessing structures such as processing unit 1820 (e.g., executinginstructions stored in memory 1822 as shown in FIG. 11. It should beunderstood, however, that these are merely examples of structures thatmay be used to execute actions shown in blocks 302 and 304, and claimedsubject matter is not limited in this respect.

At block 402, an initiating STA may receive an FTM message from aresponding STA. The FTM message received at block 402 may be an FTMmessage such as that transmitted at block 304 by having at least a firstfield expressing a time of departure of the FTM message and at least asecond field expressing a maximum error in a value expressed in thefirst field in five bits or less. Block 404 may then decode the secondfield to determine the maximum error in the value expressed in the firstfield as being as large as 1.0 msec. In particular implementations,actions set forth at blocks 402 and 404 may be performed using any oneof several structures such as, for example, wireless transceiver 1121 incombination with processing structures such as generalpurpose/application processor 1111, DSP(s) 1112 and/or modem processor1166 (e.g., executing instructions stored in memory 1140) as shown inFIG. 10, or communication interface 1830 in combination with processingstructures such as processing unit 1820 (e.g., executing instructionsstored in memory 1822 as shown in FIG. 11. It should be understood,however, that these are merely examples of structures that may be usedto execute actions shown in blocks 402 and 404, and claimed subjectmatter is not limited in this respect.

According to an embodiment, a five-bit field in a FTM measurementmessage (e.g., an FTM message transmitted at block or received at block402) may have any one of thirty-two possible states having binaryrepresentations from “00000” (representing a binary value of zero) to“11111” (representing a binary value of thirty-one). These differentpossible states may be mapped to a particular maximum error of a TOA orTOD value (e.g., expressed in a different field in the same FTM message)according to expression (1) as follows:

$\begin{matrix}{E_{\max} = \begin{Bmatrix}{{unknown},} & {{{Max}\mspace{14mu} {Error}} = 0} \\{2^{({{{Max}\mspace{14mu} {Error}} - 1})},} & {{{Max}\mspace{14mu} {Error}} = {1\text{:}30}} \\{{\geq 2^{30}},} & {{{Max}\mspace{14mu} {Error}} = 31}\end{Bmatrix}} & (1)\end{matrix}$

In an embodiment, a STA receiving an FTM message with a “Max Error” in afive-bit field expressing an error in a TOA or TOD value may decode “MaxError” according to expression (1) (e.g., at block 404) to determine themaximum error E_(max). Here, a value of Max Error=00000 in an errorfield indicates that a maximum error is unknown while a value of MaxError=11111 in an error field indicates that a maximum error is greaterthan 2³⁰ or 1073741824 psec. A value of Max Error=00001 (representing abinary value of one) to 11110 (representing a binary value of 31)indicates a maximum error of 2^((Max Error−1)) psec. Expression (1) mayexpress a maximum error in TOA or TOD as small as 1.0 ps and as large as1.0 msec with only five bits. This is shown in a particular example ofan FTM message shown in FIG. 5 at field Max TOD Error Exponent and fieldMax TOA Error Exponent, each made up of five bits to express a value forE_(max) as an exponent according to expression (1).

According to an embodiment, an RTT measurement computed at an initiatingSTA may be used for obtaining an estimated location of the initiatingSTA using techniques described above such as trilateration. In otherimplementations, an RTT measurement computed (and/or range computedbased on one or more RTT measurements) at an initiating STA may beshared with a responding STA (participating in obtaining fine timingmeasurements used in computing RTT). In one embodiment, a fine timingmeasurement request message may comprise many fields including a“trigger” field in which an initiating STA may characterize atransaction between the initiating STA and a responding STA in obtaininga fine timing measurement. In a particular implementation, an initiatingSTA may specify a particular value in a trigger field of a fine timingmeasurement request message (e.g., two) indicating that the initiatingSTA is able and willing to share one or more computed RTT measurement(and/or range computed from RTT measurements) with a recipientresponding STA. This is illustrated in the signal flow of FIG. 6. Asshown, an initiating STA transmits a fine timing measurement requestmessage 602 specifying a value of two in a trigger field. In asubsequent exchange of timing measurement messages 604 and ACK messages606, the initiating STA may compute an RTT value as discussed above.Following an ACK message 606 transmitted by the initiating STA inresponse to receiving a final fine timing measurement message 604 (e.g.,transporting values for t1 and t4), the initiating STA may transmit anFTM range report message 608 containing a value for RTT (and/or range)computed based, at least in part, on fine timing measurements receivedfrom the responding STA. In this context, an “FTM range report message”comprises a message including one or more fields expressing anindication of a range between two devices computed based, at least inpart, on a message transmitted between the two devices.

According to an embodiment, an FTM range report message transmitted froma first STA may include measurements of range between the first STA andone or more neighboring second STAs. For each of the second STAs, theFTM range report message may comprise a field identifying the second STA(e.g., BSSID), a field providing a range value and a field expressing amaximum range error. FIGS. 7 and 8 illustrated processes for providingan FTM range report message and processing an FTM range report message.At block 702, an initiating STA may receive one or more FTM messages(e.g., FTM messages 604 transmitted from a responding STA). At block704, the initiating STA may transmit an FTM range report message (e.g.,FTM range report message 608) comprising at least a first fieldcomprising a range field and at least one second field. The range fieldmay comprise one or more values indicative of a range from theinitiating STA to a device transmitting the one or more FTM messagescomputed using any one of several technique discussed above. Inparticular implementations, actions set forth at blocks 702 and 704 maybe performed using any one of several structures such as, for example,wireless transceiver 1121 in combination with processing structures suchas general purpose/application processor 1111, DSP(s) 1112 and/or modemprocessor 1166 (e.g., executing instructions stored in memory 1140) asshown in FIG. 10, or communication interface 1830 in combination withprocessing structures such as processing unit 1820 (e.g., executinginstructions stored in memory 1822 as shown in FIG. 11. It should beunderstood, however, that these are merely examples of structures thatmay be used to execute actions shown in blocks 702 and 704, and claimedsubject matter is not limited in this respect.

FIG. 9 shows an example of fields in an FTM range report messagetransmitted at block 704 that include a range field labeled “Range.” Inaddition, the second field comprises one or more values indicative of amaximum range error in the one or more values indicative of the range inthe range field. FIG. 9 shows an example of field comprising one or morevalues indicative of a maximum range error labeled “Max Range ErrorExponent.” According to an embodiment, this maximum range error may beexpressed in five bits or less and express a maximum range error of upto at least 2000 m.

In the particular implementation of FIG. 9, the field “Max Range ErrorExponent” expressing a maximum range error may comprise an exponentvalue according to a the following providing obtained from according toexpression (2) as follows:

$\begin{matrix}{{{Range}\mspace{14mu} {Error}_{\max}} = \begin{Bmatrix}{{unknown},{{{Max}\mspace{14mu} {Range}\mspace{14mu} {Error}\mspace{14mu} {Exponent}} = 0}} \\\begin{matrix}{{2^{({{{Max}\mspace{14mu} {Range}\mspace{14mu} {Error}\mspace{14mu} {Exponent}} - 13})}\mspace{14mu} m},} \\{{{Max}\mspace{14mu} {Range}\mspace{14mu} {Error}\mspace{14mu} {Exponent}} = {1\text{:}24}}\end{matrix} \\{{\geq {4096\mspace{14mu} m}},{{{Max}\mspace{14mu} {Range}\mspace{14mu} {Error}\mspace{14mu} {Exponent}} = 25}}\end{Bmatrix}} & (2)\end{matrix}$

As shown in FIG. 9, value for Max Range Error Exponent may be expressedin a single octet of an FTM range report message. According to anembodiment, the five least significant bits of a single octet allocatedfor the Max Range Error Exponent field may be used to express valuesfrom zero (expressed as “00000” in binary) to twenty-five (expressed as“11001” in binary). According to expression (2) value of fourteen in thea five-bit field for Max Range Error Exponent field (“01110”) indicatesa maximum range error as +1-2.0 m.

In the process of FIG. 8, a responding STA may receive an FTM rangereport message (e.g., FTM range report message 608) at block 802. TheFTM range report message received at block 802 may comprises fields asshown in the example of FIG. 9, and may comprise a range field and atleast one other field capable of expressing a maximum range error infive bits or less. At block 804, the responding STA may decode the fieldcapable of expressing a maximum range field in five bits or less todetermine a maximum range error of up to at least 2000 m. For example,block 804 may comprise decoding a five-bit value in the field “Max RangeError Exponent” shown in FIG. 9 to determine a maximum range error RangeError_(max) according to expression (2). In particular implementations,actions set forth at blocks 802 and 804 may be performed using any oneof several structures such as, for example, wireless transceiver 1121 incombination with processing structures such as generalpurpose/application processor 1111, DSP(s) 1112 and/or modem processor1166 (e.g., executing instructions stored in memory 1140) as shown inFIG. 10, or communication interface 1830 in combination with processingstructures such as processing unit 1820 (e.g., executing instructionsstored in memory 1822 as shown in FIG. 11. It should be understood,however, that these are merely examples of structures that may be usedto execute actions shown in blocks 802 and 804, and claimed subjectmatter is not limited in this respect.

FIG. 10 is a schematic diagram of a mobile device according to anembodiment. Mobile device 100 (FIG. 1) may comprise one or more featuresof mobile device 1100 shown in FIG. 10. In certain embodiments, mobiledevice 1100 may also comprise a wireless transceiver 1121 which iscapable of transmitting and receiving wireless signals 1123 via wirelessantenna 1122 over a wireless communication network. Wireless transceiver1121 may be connected to bus 1101 by a wireless transceiver businterface 1120. Wireless transceiver bus interface 1120 may, in someembodiments be at least partially integrated with wireless transceiver1121. Some embodiments may include multiple wireless transceivers 1121and wireless antennas 1122 to enable transmitting and/or receivingsignals according to a corresponding multiple wireless communicationstandards such as, for example, versions of IEEE Std. 802.11, CDMA,WCD-MA, LTE, UMTS, GSM, AMPS, Zigbee and Bluetooth, just to name a fewexamples.

Mobile device 1100 may further comprise a clock 1142 comprisingcircuitry, registers, memory, etc. that is capable of advancing andmaintaining a clock state. In a particular implementation, a clock statemay be advanced by incrementing a counter or other value on setincrement cycles (e.g., in response to an oscillating signal). Inparticular implementations, clock 1142 may comprise registers,oscillators, input terminals output terminals, etc. capable of providingvalues indicative of a clock state. In particular embodiments, a clockstate maintained at clock 1142 may be used to control processes toexecute application functions on in a coordinated fashion on generalpurpose/application processor 1111, DSP(s) 1112, etc. As pointed outabove, a clock state maintained at clock 1142 may be synchronized withclock states maintained by devices other than mobile device 1100.

Mobile device 1100 may also comprise SPS receiver 1155 capable ofreceiving and acquiring SPS signals 1159 via SPS antenna 1158. SPSreceiver 1155 may also process, in whole or in part, acquired SPSsignals 1159 for estimating a location of mobile device 1000. In someembodiments, general-purpose processor(s) 1111, memory 1140, DSP(s) 1112and/or specialized processors (not shown) may also be utilized toprocess acquired SPS signals, in whole or in part, and/or calculate anestimated location of mobile device 1100, in conjunction with SPSreceiver 1155. Storage of SPS or other signals for use in performingpositioning operations may be performed in memory 1140 or registers (notshown).

Also shown in FIG. 10, mobile device 1100 may comprise digital signalprocessor(s) (DSP(s)) 1112 connected to the bus 1101 by a bus interface,general-purpose processor(s) 1111 connected to the bus 1101 by a businterface 1110 and memory 1140. In a particular implementation, the businterface may be integrated with the DSP(s) 1112, general-purposeprocessor(s) 1111 and memory 1140. In various embodiments, functions maybe performed in response execution of one or more machine-readableinstructions stored in memory 1140 such as on a computer-readablestorage medium, such as RAM, ROM, FLASH, or disc drive, just to name afew example. The one or more instructions may be executable bygeneral-purpose processor(s) 1111, specialized processors, or DSP(s)1112. Memory 1140 may comprise a non-transitory processor-readablememory and/or a computer-readable memory that stores software code(programming code, instructions, etc.) that are executable byprocessor(s) 1111 and/or DSP(s) 1112 to perform functions describedherein. In a particular implementation, wireless transceiver 1121 maycommunicate with general-purpose processor(s) 1111 and/or DSP(s) 1112through bus 1101 to enable mobile device 1100 to be configured as awireless STA as discussed above. General-purpose processor(s) 1111and/or DSP(s) 1112 may execute instructions to execute one or moreaspects of processes discussed above in connection with FIGS. 3, 4, 7and 8.

Also shown in FIG. 4, a user interface 1135 may comprise any one ofseveral devices such as, for example, a speaker, microphone, displaydevice, vibration device, keyboard, touch screen, just to name a fewexamples. In a particular implementation, user interface 1135 may enablea user to interact with one or more applications hosted on mobile device1100. For example, devices of user interface 1135 may store analog ordigital signals on memory 1140 to be further processed by DSP(s) 1112 orgeneral purpose/application processor 1111 in response to action from auser. Similarly, applications hosted on mobile device 1100 may storeanalog or digital signals on memory 1140 to present an output signal toa user. In another implementation, mobile device 1100 may optionallyinclude a dedicated audio input/output (I/O) device 1170 comprising, forexample, a dedicated speaker, microphone, digital to analog circuitry,analog to digital circuitry, amplifiers and/or gain control. It shouldbe understood, however, that this is merely an example of how an audioI/O may be implemented in a mobile device, and that claimed subjectmatter is not limited in this respect. In another implementation, mobiledevice 1100 may comprise touch sensors 1162 responsive to touching orpressure on a keyboard or touch screen device.

Mobile device 1100 may also comprise a dedicated camera device 1164 forcapturing still or moving imagery. Dedicated camera device 1164 maycomprise, for example an imaging sensor (e.g., charge coupled device orCMOS imager), lens, analog to digital circuitry, frame buffers, just toname a few examples. In one implementation, additional processing,conditioning, encoding or compression of signals representing capturedimages may be performed at general purpose/application processor 1111 orDSP(s) 1112. Alternatively, a dedicated video processor 1168 may performconditioning, encoding, compression or manipulation of signalsrepresenting captured images. Additionally, dedicated video processor1168 may decode/decompress stored image data for presentation on adisplay device (not shown) on mobile device 1100.

Mobile device 1100 may also comprise sensors 1160 coupled to bus 1101which may include, for example, inertial sensors and environmentsensors. Inertial sensors of sensors 1160 may comprise, for exampleaccelerometers (e.g., collectively responding to acceleration of mobiledevice 1100 in three dimensions), one or more gyro-scopes or one or moremagnetometers (e.g., to support one or more compass applications).Environment sensors of mobile device 1100 may comprise, for example,temperature sensors, barometric pressure sensors, ambient light sensors,camera imagers, microphones, just to name few examples. Sensors 1160 maygenerate analog or digital signals that may be stored in memory 1140 andprocessed by DPS(s) or general purpose/application processor 1111 insupport of one or more applications such as, for example, applicationsdirected to positioning or navigation operations.

In a particular implementation, mobile device 1100 may comprise adedicated modem processor 1166 capable of performing baseband processingof signals received and downconverted at wireless transceiver 1121 orSPS receiver 1155. Similarly, dedicated modem processor 1166 may performbaseband processing of signals to be up-converted for transmission bywireless transceiver 1121. In alternative implementations, instead ofhaving a dedicated modem processor, baseband processing may be performedby a general purpose processor or DSP (e.g., general purpose/applicationprocessor 1111 or DSP(s) 1112). It should be understood, however, thatthese are merely examples of structures that may perform basebandprocessing, and that claimed subject matter is not limited in thisrespect.

FIG. 11 is a schematic diagram illustrating an example system 1800 thatmay include one or more devices configurable to implement techniques orprocesses described above, for example, in connection with FIG. 1.System 1800 may include, for example, a first device 1802, a seconddevice 1804, and a third device 1806, which may be operatively coupledtogether through a wireless communications network. In an aspect, firstdevice 1802 may comprise an access point as shown, for example. Seconddevice 1804 may comprise an access point (e.g., local transceiver 115)and third device 1806 may comprise a mobile station or mobile device, inan aspect. Also, in an aspect, devices 1802, 1804 and 1802 may beincluded in a wireless communications network may comprise one or morewireless access points, for example. However, claimed subject matter isnot limited in scope in these respects.

First device 1802, second device 1804 and third device 1806, as shown inFIG. 11, may be representative of any device, appliance or machine thatmay be configurable to exchange data over a wireless communicationsnetwork. By way of example but not limitation, any of first device 1802,second device 1804, or third device 1806 may include: one or morecomputing devices or platforms, such as, e.g., a desktop computer, alaptop computer, a workstation, a server device, or the like; one ormore personal computing or communication devices or appliances, such as,e.g., a personal digital assistant, mobile communication device, or thelike; a computing system or associated service provider capability, suchas, e.g., a database or data storage service provider/system, a networkservice provider/system, an Internet or intranet serviceprovider/system, a portal or search engine service provider/system, awireless communication service provider/system; or any combinationthereof. Any of the first, second, and third devices 1802, 1804, and1806, respectively, may comprise one or more of an access point or amobile device in accordance with the examples described herein.

Similarly, a wireless communications network, as shown in FIG. 11, isrepresentative of one or more communication links, processes, orresources configurable to support the exchange of data between at leasttwo of first device 1802, second device 1804, and third device 1806. Byway of example but not limitation, a wireless communications network mayinclude wireless or wired communication links, telephone ortelecommunications systems, data buses or channels, optical fibers,terrestrial or space vehicle resources, local area networks, wide areanetworks, intranets, the Internet, routers or switches, and the like, orany combination thereof. As illustrated, for example, by the dashedlined box illustrated as being partially obscured of third device 1806,there may be additional like devices operatively coupled to wirelesscommunications network 1800.

It is recognized that all or part of the various devices and networksshown in FIG. 11, and the processes and methods as further describedherein, may be implemented using or otherwise including hardware,firmware, software, or any combination thereof.

Thus, by way of example but not limitation, second device 1804 mayinclude at least one processing unit 1820 that is operatively coupled toa memory 1822 through a bus 1828.

Processing unit 1820 is representative of one or more circuitsconfigurable to perform at least a portion of a data computing procedureor process. By way of example but not limitation, processing unit 1820may include one or more processors, controllers, microprocessors,microcontrollers, application specific integrated circuits, digitalsignal processors, programmable logic devices, field programmable gatearrays, and the like, or any combination thereof.

Memory 1822 is representative of any data storage mechanism. Memory 1822may include, for example, a primary memory 1824 or a secondary memory1826. Primary memory 1824 may include, for example, a random accessmemory, read only memory, etc. While illustrated in this example asbeing separate from processing unit 1820, it should be understood thatall or part of primary memory 1824 may be provided within or otherwiseco-located/coupled with processing unit 1820. In a particularimplementation, memory 1822 and processing unit 1820 may be configuredto execute one or more aspects of process discussed above in connectionwith FIGS. 3, 4, 7 and 8.

Secondary memory 1826 may include, for example, the same or similar typeof memory as primary memory or one or more data storage devices orsystems, such as, for example, a disk drive, an optical disc drive, atape drive, a solid state memory drive, etc. In certain implementations,secondary memory 1826 may be operatively receptive of, or otherwiseconfigurable to couple to, a computer-readable medium 1840.Computer-readable medium 1840 may include, for example, anynon-transitory medium that can carry or make accessible data, code orinstructions for one or more of the devices in system 1800.Computer-readable medium 1840 may also be referred to as a storagemedium.

Second device 1804 may further comprise a clock 1850 comprisingcircuitry, registers, memory, etc. that is capable of advancing andmaintaining a clock state. In a particular implementation, a clock statemay be advanced by incrementing a counter or other value on setincrement cycles (e.g., in response to an oscillating signal). Inparticular implementations, clock 1850 may comprise registers,oscillators, input terminals output terminals, etc. capable of providingvalues indicative of a clock state. In particular embodiments, a clockstate maintained at clock 1850 may be used to control processes toexecute application functions on in a coordinated fashion on generalpurpose/application processor 1111, DSP(s) 1112, etc. As pointed outabove, a clock state maintained at clock 1850 may be synchronized withclock states maintained by devices other than second device 1804 (e.g.,first device 1802 and third device 1806).

Second device 1804 may include, for example, a communication interface1830 that provides for or otherwise supports the operative coupling ofsecond device 1804 to a wireless communications network at least throughan antenna 1808. By way of example but not limitation, communicationinterface 1830 may include a network interface device or card, a modem,a router, a switch, a transceiver, and the like. In other alternativeimplementations, communication interface 1830 may comprise a wired/LANinterface, wireless LAN interface (e.g., IEEE std. 802.11 wirelessinterface) and/or a wide area network (WAN) air interface. In aparticular implementation, antenna 1808 in combination withcommunication interface 1830 may be used to implement transmission andreception of signals as illustrated in FIGS. 3, 4, 7 and 8.

In one particular implementation, transmission of an ACK message inresponse to a FTM measurement request message may be performed atcommunication interface 1830 without instruction or initiation fromprocessing unit 1820. On the other hand, an FTM range report message maybe formed at a programmable device such as processing unit 1820 (e.g.,from execution of one or more machine-readable instructions stored inmemory 1822).

Second device 1804 may include, for example, an input/output device1832. Input/output device 1832 is representative of one or more devicesor features that may be configurable to accept or otherwise introducehuman or machine inputs, or one or more devices or features that may beconfigurable to deliver or otherwise provide for human or machineoutputs. By way of example but not limitation, input/output device 1832may include an operatively configured display, speaker, keyboard, mouse,track-ball, touch screen, data port, etc.

One particular embodiment is directed to a method, at a first wirelessstation, comprising: transmitting a fine timing measurement (FTM) rangereport message comprising at least a range field and at least one otherfield, the at least one other field being capable of expressing amaximum range error in five bits or less of up to at least 2000 m. Inone particular implementation, the at least one other field expressesthe maximum range error as an exponent. In another particularimplementation, the at least one other field is further capable ofexpressing the maximum range error at least as small as 0.00025 m.

Another particular embodiment is directed to a non-transitory storagemedium having computer-readable instructions stored thereon which areexecutable by a process of a first wireless station (STA) to: initiatetransmission of a fine timing measurement (FTM) message through awireless transmitter comprising at least a range field and at least oneother field, the at least on other field being capable of expressing amaximum range error in five bits or less of up to at least 2000 m. Inone particular implementation, the at least one other field expressesthe maximum range error as an exponent. In another particularimplementation, the at least one other field is further capable ofexpressing the maximum range error at least as small as 0.00025 m.

Another particular embodiment is directed to a first wireless station(STA), comprising: a wireless transceiver to transmit messages to awireless communication network; and one or more processors coupled tothe wireless transmitter, the one or more processors being configuredto: initiate transmission of a fine timing measurement (FTM) messagethrough the wireless transmitter comprising at least a range field andat least one other field, the at least one other field being capable ofexpressing a maximum range error in five bits or less of up to at least2000 m. In one particular implementation, the at least one other fieldexpresses the maximum range error as an exponent. In another particularimplementation, the at least one other field is further capable ofexpressing the maximum range error at least as small as 0.00025 m.

Another particular embodiment is directed to a first wireless station,comprising: means for receiving one or more fine timing measurement(FTM) messages; and means for transmitting an FTM range report messagebased, at least in part, on the received one or more FTM messages, theFTM range report message comprising at least a range field and at leastone other field, the at least one other field being capable ofexpressing a maximum range error in five bits or less of up to at least2000 m. In one particular implementation, the at least one other fieldexpresses the maximum range error as an exponent. In another particularimplementation, the at least one other field is further capable ofexpressing the maximum range error at least as small as 0.00025 m.

Another particular embodiment is directed to a first wireless station(STA), comprising: receiving a fine timing measurement (FTM) messagecomprising at least a time of departure (TOD) field and at least oneother field, the at least one other field expressing a maximum TOD errorin five bits or less; and decoding the at least one other field todetermine the maximum TOD error as large as 1.0 msec. In one particularimplementation, the FTM message is transmitted by a second STA inresponse to receipt of a FTM request message transmitted by the firstSTA. In another particular implementation, the at least one other fieldexpresses the maximum TOD error as an exponent. In another particularimplementation, the FTM message further comprises a time of arrival(TOA) field and at least one other field expressing a maximum TOA errorin five bits or less, method further comprising decoding the at leastone other field to determine the maximum TOA error as large as 1.0 msec.In another particular implementation, the at least one other field beingcapable of expressing the maximum TOA error as small as 1.0 psec. Inanother particular implementation, the at least one other field isfurther capable of expressing the maximum TOD error as small as 1.0psec.

Another particular implementation is directed to a first wirelessstation (STA), comprising: a wireless transceiver to receive messagesfrom a wireless communication network; and one or more processorsconfigured to: obtain a fine timing measurement (FTM) message receivedat the wireless receiver comprising at least a time of departure (TOD)field and at least one other field, the at least one other fieldexpressing a maximum TOD error in five bits or less; and decode the atleast one other field to determine the maximum TOD error as large as 1.0msec. In one particular implementation, the FTM message is transmittedby a second STA in response to receipt of a FTM request messagetransmitted by the first STA. In another particular implementation, theat least one other field expresses the maximum TOD error as an exponent.In another particular implementation, the FTM message further comprisesa time of arrival (TOA) field and at least one other field expressing amaximum TOA error in five bits or less, and wherein the one or moreprocessors are further configured to decode the at least one other fieldto determine the maximum TOA error as large as 1.0 msec. In anotherparticular implementation, the at least one other field being capable ofexpressing the maximum TOA error as small as 1.0 psec. In anotherparticular implementation, the at least one other field is furthercapable of expressing the maximum TOD error as small as 1.0 psec.

In another particular embodiment, a first wireless station (STA),comprising: means for receiving a fine timing measurement (FTM) messagecomprising at least a time of departure (TOD) field and at least oneother field, the at least one other field expressing a maximum TOD errorin five bits or less; and means for decoding the at least one otherfield to determine the maximum TOD error as large as 1.0 msec. In oneparticular implementation, the FTM message is transmitted by a secondSTA in response to receipt of a FTM request message transmitted by thefirst STA. In another particular implementation, the at least one otherfield expresses the maximum TOD error as an exponent. In anotherparticular implementation, the FTM message further comprises a time ofarrival (TOA) field and at least one other field expressing a maximumTOA error in five bits or less, the first STA further comprising meansfor decoding the at least one other field to determine the maximum TOAerror as large as 1.0 msec. In another particular implementation, the atleast one other field being capable of expressing the maximum TOA erroras small as 1.0 psec. In another particular implementation, the at leastone other field is further capable of expressing the maximum TOD erroras small as 1.0 psec.

Another particular implementation is directed to a non-transitorystorage medium having computer-readable instructions stored thereonwhich are executable by a processor of a first wireless station (STA)to: obtain a fine timing measurement (FTM) message received at awireless transmitter comprising at least a time of departure (TOD) fieldand at least one other field, the at least one other field expressing amaximum TOD error in five bits or less; and decode the at least oneother field to determine the maximum TOD error as large as 1.0 msec. Inone particular implementation, the FTM message is transmitted by asecond STA in response to receipt of a FTM request message transmittedby the first STA. In another particular implementation, the at least oneother field expresses the maximum TOD error as an exponent. In anotherparticular implementation, the FTM message further comprises a time ofarrival (TOA) field and at least one other field expressing a maximumTOA error in five bits or less, and wherein the instructions are furtherexecutable by the processor to decode the at least one other field todetermine the maximum TOA error as large as 1.0 msec. In anotherparticular implementation, the at least one other field being capable ofexpressing the maximum TOA error as small as 1.0 psec. In anotherparticular implementation, the at least one other field is furthercapable of expressing the maximum TOD error as small as 1.0 psec.

Another particular embodiment is directed to a method, at a firstwireless station, comprising: receiving a fine timing measurement (FTM)range report message comprising at least a range field and at least oneother field, the at least one other field being capable of expressing amaximum range error in five bits or less; and decoding the at least oneother field to determine the maximum range error up to at least 2000 m.In a particular implementation, the at least one other field expressesthe maximum range error as an exponent. In a particular implementation,the at least one other field is further capable of expressing themaximum range error at least as small as 0.00025 m.

In another particular embodiment is directed to a non-transitory storagemedium having computer-readable instructions stored thereon which areexecutable by a process of a first wireless station (STA) to: obtain afine timing measurement (FTM) message received at a wireless receivercomprising at least a range field and at least one other field, the atleast one other field being capable of expressing a maximum range errorin five bits or less; and decode the at least one other field todetermine the maximum range error up to at least 2000 m. In oneparticular implementation, the at least one other field expresses themaximum range error as an exponent. In another particularimplementation, the instructions are further executable to decode the atleast one other field to determine the maximum range error at least assmall as 0.00025 m.

Another particular embodiment is directed to a first wireless station(STA), comprising: a wireless receiver to receive messages from awireless communication network; and one or more processors coupled tothe wireless receiver, the one or more processors being configured to:obtain a fine timing measurement (FTM) message received at the wirelessreceiver comprising at least a range field and at least one other field,the at least one other field being capable of expressing a maximum rangeerror in five bits or less; and decode the at least one other field todetermine the maximum range error up to at least 2000 m. In oneparticular implementation, the at least one other field expresses themaximum range error as an exponent. In another particularimplementation, the instructions are further executable by the processorto decode the at least one other field to determine the maximum rangeerror at least as small as 0.00025 m.

Another particular embodiment is directed to a first wireless station,comprising: means for receiving a fine timing measurement (FTM) rangereport message comprising at least a range field and at least one otherfield, the at least one other field being capable of expressing amaximum range error in five bits or less; and means for decoding the atleast one other field to determine the maximum range error up to atleast 2000 m. In one particular implementation, the at least one otherfield expresses the maximum range error as an exponent. In anotherparticular implementation, the at least one other field is furthercapable of expressing the maximum range error at least as small as0.00025 m.

As used herein, the term “access point” is meant to include any wirelesscommunication station and/or device used to facilitate communication ina wireless communications system, such as, for example, a wireless localarea network, although the scope of claimed subject matter is notlimited in this respect. In another aspect, an access point may comprisea wireless local area network (WLAN) access point, for example. Such aWLAN may comprise a network compatible and/or compliant with one or moreversions of IEEE standard 802.11 in an aspect, although the scope ofclaimed subject matter is not limited in this respect. A WLAN accesspoint may provide communication between one or more mobile devices and anetwork such as the Internet, for example.

As used herein, the term “mobile device” refers to a device that mayfrom time to time have a position location that changes. The changes inposition location may comprise changes to direction, distance,orientation, etc., as a few examples. In particular examples, a mobiledevice may comprise a cellular telephone, wireless communication device,user equipment, laptop computer, other personal communication system(PCS) device, personal digital assistant (PDA), personal audio device(PAD), portable navigational device, and/or other portable communicationdevices. A mobile device may also comprise a processor and/or computingplatform adapted to perform functions controlled by machine-readableinstructions.

The methodologies described herein may be implemented by various meansdepending upon applications according to particular examples. Forexample, such methodologies may be implemented in hardware, firmware,software, or combinations thereof. In a hardware implementation, forexample, a processing unit may be implemented within one or moreapplication specific integrated circuits (“ASICs”), digital signalprocessors (“DSPs”), digital signal processing devices (“DSPDs”),programmable logic devices (“PLDs”), field programmable gate arrays(“FPGAs”), processors, controllers, micro-controllers, microprocessors,electronic devices, other devices units de-signed to perform thefunctions described herein, or combinations thereof.

Algorithmic descriptions and/or symbolic representations are examples oftechniques used by those of ordinary skill in the signal processingand/or related arts to convey the substance of their work to othersskilled in the art. An algorithm is here, and generally, is consideredto be a self-consistent sequence of operations and/or similar signalprocessing leading to a desired result. In this context, operationsand/or processing involve physical manipulation of physical quantities.Typically, although not necessarily, such quantities may take the formof electrical and/or magnetic signals and/or states capable of beingstored, transferred, combined, compared, processed or otherwisemanipulated as electronic signals and/or states representing variousforms of content, such as signal measurements, text, images, video,audio, etc. It has proven convenient at times, principally for reasonsof common usage, to refer to such physical signals and/or physicalstates as bits, values, elements, symbols, characters, terms, numbers,numerals, messages, frames, measurements, content and/or the like. Itshould be understood, however, that all of these and/or similar termsare to be associated with appropriate physical quantities and are merelyconvenient labels. Unless specifically stated otherwise, as apparentfrom the preceding discussion, it is appreciated that throughout thisspecification discussions utilizing terms such as “processing,”“computing,” “calculating,” “determining”, “establishing”, “obtaining”,“identifying”, “selecting”, “generating”, and/or the like may refer toactions and/or processes of a specific apparatus, such as a specialpurpose computer and/or a similar special purpose computing and/ornetwork device. In the context of this specification, therefore, aspecial purpose computer and/or a similar special purpose computingand/or network device is capable of processing, manipulating and/ortransforming signals and/or states, typically represented as physicalelectronic and/or magnetic quantities within memories, registers, and/orother storage devices, transmission devices, and/or display devices ofthe special purpose computer and/or similar special purpose computingand/or network device. In the context of this particular patentapplication, as mentioned, the term “specific apparatus” may include ageneral purpose computing and/or network device, such as a generalpurpose computer, once it is programmed to perform particular functionspursuant to instructions from program software.

In some circumstances, operation of a memory device, such as a change instate from a binary one to a binary zero or vice-versa, for example, maycomprise a transformation, such as a physical transformation. Withparticular types of memory devices, such a physical transformation maycomprise a physical transformation of an article to a different state orthing. For example, but without limitation, for some types of memorydevices, a change in state may involve an accumulation and/or storage ofcharge or a release of stored charge. Likewise, in other memory devices,a change of state may comprise a physical change, such as atransformation in magnetic orientation and/or a physical change and/ortransformation in molecular structure, such as from crystalline toamorphous or vice-versa. In still other memory devices, a change inphysical state may involve quantum mechanical phenomena, such as,superposition, entanglement, and/or the like, which may involve quantumbits (qubits), for example. The foregoing is not intended to be anexhaustive list of all examples in which a change in state form a binaryone to a binary zero or vice-versa in a memory device may comprise atransformation, such as a physical transformation. Rather, the foregoingis intended as illustrative examples.

Wireless communication techniques described herein may be in connectionwith various wireless communications networks such as a wireless widearea network (“WWAN”), a wireless local area network (“WLAN”), awireless personal area network (WPAN), and so on. In this context, a“wireless communication network” comprises multiple devices or nodescapable of communicating with one another through one or more wirelesscommunication links. As shown in FIG. 1, for example, a wirelesscommunication network may comprise two or more devices from mobiledevices 100 a, 100 b, 115 a and 115 b. The term “network” and “system”may be used interchangeably herein. A WWAN may be a Code DivisionMultiple Access (“CDMA”) network, a Time Division Multiple Access(“TDMA”) network, a Frequency Division Multiple Access (“FDMA”) network,an Orthogonal Frequency Division Multiple Access (“OFDMA”) network, aSingle-Carrier Frequency Division Multiple Access (“SC-FDMA”) network,or any combination of the above networks, and so on. A CDMA network mayimplement one or more radio access technologies (“RATs”) such ascdma2000, Wideband-CDMA (“W-CDMA”), to name just a few radiotechnologies. Here, cdma2000 may include technologies implementedaccording to IS-95, IS-2000, and IS-856 standards. A TDMA network mayimplement Global System for Mobile Communications (“GSM”), DigitalAdvanced Mobile Phone System (“D-AMPS”), or some other RAT. GSM andW-CDMA are described in documents from a consortium named “3rdGeneration Partnership Project” (“3GPP”). Cdma2000 is described indocuments from a consortium named “3rd Generation Partnership Project 2”(“3GPP2”). 3GPP and 3GPP2 documents are publicly available. 4G Long TermEvolution (“LTE”) communications networks may also be implemented inaccordance with claimed subject matter, in an aspect. A WLAN maycomprise an IEEE 802.11x network, and a WPAN may comprise a Bluetoothnetwork, an IEEE 802.15x, for example. Wireless communicationimplementations described herein may also be used in connection with anycombination of WWAN, WLAN or WPAN.

In another aspect, as previously mentioned, a wireless transmitter oraccess point may comprise a femtocell, utilized to extend cellulartelephone service into a business or home. In such an implementation,one or more mobile devices may communicate with a femtocell via a codedivision multiple access (“CDMA”) cellular communication protocol, forexample, and the femtocell may provide the mobile device access to alarger cellular telecommunication network by way of another broadbandnetwork such as the Internet.

Techniques described herein may be used with an SPS that includes anyone of several GNSS and/or combinations of GNSS. Furthermore, suchtechniques may be used with positioning systems that utilize terrestrialtransmitters acting as “pseudolites”, or a combination of SVs and suchterrestrial transmitters. Terrestrial transmitters may, for example,include ground-based transmitters that broadcast a PN code or otherranging code (e.g., similar to a GPS or CDMA cellular signal). Such atransmitter may be assigned a unique PN code so as to permitidentification by a remote receiver. Terrestrial transmitters may beuseful, for example, to augment an SPS in situations where SPS signalsfrom an orbiting SV might be unavailable, such as in tunnels, mines,buildings, urban canyons or other enclosed areas. Another implementationof pseudolites is known as radio-beacons. The term “SV”, as used herein,is intended to include terrestrial transmitters acting as pseudolites,equivalents of pseudolites, and possibly others. The terms “SPS signals”and/or “SV signals”, as used herein, is intended to include SPS-likesignals from terrestrial transmitters, including terrestrialtransmitters acting as pseudolites or equivalents of pseudolites.

Likewise, in this context, the terms “coupled”, “connected,” and/orsimilar terms are used generically. It should be understood that theseterms are not intended as synonyms. Rather, “connected” is usedgenerically to indicate that two or more components, for example, are indirect physical, including electrical, contact; while, “coupled” is usedgenerically to mean that two or more components are potentially indirect physical, including electrical, contact; however, “coupled” isalso used generically to also mean that two or more components are notnecessarily in direct contact, but nonetheless are able to co-operateand/or interact. The term coupled is also understood generically to meanindirectly connected, for example, in an appropriate context.

The terms, “and”, “or”, “and/or” and/or similar terms, as used herein,include a variety of meanings that also are expected to depend at leastin part upon the particular context in which such terms are used.Typically, “or” if used to associate a list, such as A, B or C, isintended to mean A, B, and C, here used in the inclusive sense, as wellas A, B or C, here used in the exclusive sense. In addition, the term“one or more” and/or similar terms is used to describe any feature,structure, and/or characteristic in the singular and/or is also used todescribe a plurality and/or some other combination of features,structures and/or characteristics. Likewise, the term “based on” and/orsimilar terms are understood as not necessarily intending to convey anexclusive set of factors, but to allow for existence of additionalfactors not necessarily expressly described. Of course, for all of theforegoing, particular context of description and/or usage provideshelpful guidance regarding inferences to be drawn. It should be notedthat the following description merely provides one or more illustrativeexamples and claimed subject matter is not limited to these one or moreexamples; however, again, particular context of description and/or usageprovides helpful guidance regarding inferences to be drawn.

In this context, the term network device refers to any device capable ofcommunicating via and/or as part of a network and may comprise acomputing device. While network devices may be capable of sending and/orreceiving signals (e.g., signal packets and/or frames), such as via awired and/or wireless network, they may also be capable of performingarithmetic and/or logic operations, processing and/or storing signals,such as in memory as physical memory states, and/or may, for example,operate as a server in various embodiments. Network devices capable ofoperating as a server, or otherwise, may include, as examples, dedicatedrack-mounted servers, desktop computers, laptop computers, set topboxes, tablets, netbooks, smart phones, wearable devices, integrateddevices combining two or more features of the foregoing devices, thelike or any combination thereof. Signal packets and/or frames, forexample, may be exchanged, such as between a server and a client deviceand/or other types of network devices, including between wirelessdevices coupled via a wireless network, for example. It is noted thatthe terms, server, server device, server computing device, servercomputing platform and/or similar terms are used interchangeably.Similarly, the terms client, client device, client computing device,client computing platform and/or similar terms are also usedinterchangeably. While in some instances, for ease of description, theseterms may be used in the singular, such as by referring to a “clientdevice” or a “server device,” the description is intended to encompassone or more client devices and/or one or more server devices, asappropriate. Along similar lines, references to a “database” areunderstood to mean, one or more databases and/or portions thereof, asappropriate.

It should be understood that for ease of description a network device(also referred to as a networking device) may be embodied and/ordescribed in terms of a computing device. However, it should further beunderstood that this description should in no way be construed thatclaimed subject matter is limited to one embodiment, such as a computingdevice and/or a network device, and, instead, may be embodied as avariety of devices or combinations thereof, including, for example, oneor more illustrative examples.

References throughout this specification to one implementation, animplementation, one embodiment, an embodiment and/or the like means thata particular feature, structure, and/or characteristic described inconnection with a particular implementation and/or embodiment isincluded in at least one implementation and/or embodiment of claimedsubject matter. Thus, appearances of such phrases, for example, invarious places throughout this specification are not necessarilyintended to refer to the same implementation or to any one particularimplementation described. Furthermore, it is to be understood thatparticular features, structures, and/or characteristics described arecapable of being combined in various ways in one or more implementationsand, therefore, are within intended claim scope, for example. Ingeneral, of course, these and other issues vary with context. Therefore,particular context of description and/or usage provides helpful guidanceregarding inferences to be drawn.

While there has been illustrated and described what are presentlyconsidered to be example features, it will be understood by thoseskilled in the art that various other modifications may be made, andequivalents may be substituted, without departing from claimed subjectmatter. Additionally, many modifications may be made to adapt aparticular situation to the teachings of claimed subject matter withoutdeparting from the central concept described herein. Therefore, it isintended that claimed subject matter not be limited to the particularexamples disclosed, but that such claimed subject matter may alsoinclude all aspects falling within the scope of the appended claims, andequivalents thereof.

What is claimed is:
 1. A method, at a first wireless station (STA),comprising: transmitting a fine timing measurement (FTM) messagecomprising at least a time of departure (TOD) field and at least oneother field, the at least one other field expressing a maximum TOD errorin five bits or less, the at least one other field being capable ofexpressing the maximum TOD error as large as 1.0 msec.
 2. The method ofclaim 1, wherein the FTM message is transmitted in response to receiptof a FTM request message transmitted by a second STA.
 3. The method ofclaim 1, wherein the at least one other field expresses the maximum TODerror as an exponent.
 4. The method of claim 1, wherein the FTM messagefurther comprises a time of arrival (TOA) field and at least one otherfield expressing a maximum TOA error in five bits or less, the at leastone other field being capable of expressing the maximum TOA error aslarge as 1.0 msec.
 5. The method of claim 4, wherein the at least oneother field being capable of expressing the maximum TOA error as smallas 1.0 psec.
 6. The method of claim 1, wherein the at least one otherfield is further capable of expressing the maximum TOD error as small as1.0 psec.
 7. A first wireless station (STA), comprising: a wirelesstransceiver to transmit messages to and receive messages from a wirelesscommunication network; and one or more processors coupled to thewireless transmitter, the one or more processors being configured to:initiate transmission of a fine timing measurement (FTM) message throughthe wireless transceiver comprising at least a time of departure (TOD)field and at least one other field, the at least one other fieldexpressing a maximum TOD error in five bits or less, the at least oneother field being capable of expressing the maximum TOD error as largeas 1.0 msec.
 8. The first STA of claim 7, wherein the FTM message istransmitted in response to receipt of a FTM request message transmittedby a second STA.
 9. The first STA of claim 7, wherein the at least oneother field expresses the maximum TOD error as an exponent.
 10. Thefirst STA of claim 7, wherein the FTM message further comprises a timeof arrival (TOA) field and at least one other field expressing a maximumTOA error in five bits or less, the at least one other field beingcapable of expressing the maximum TOA error as large as 1.0 msec. 11.The first STA of claim 10, wherein the at least one other field beingcapable of expressing the maximum TOA error as small as 1.0 psec. 12.The first STA of claim 7, wherein the at least one other field isfurther capable of expressing the maximum TOD error as small as 1.0psec.
 13. A first wireless station (STA), comprising: means forreceiving a fine timing measurement (FTM) request message; and means fortransmitting an FTM message in response to the FTM request messagecomprising at least a time of departure (TOD) field and at least oneother field, the at least one other field expressing a maximum TOD errorin five bits or less, the at least one other field being capable ofexpressing the maximum TOD error as large as 1.0 msec.
 14. The first STAof claim 13, wherein the FTM message is transmitted in response toreceipt of a FTM request message transmitted by a second STA.
 15. Thefirst STA of claim 13, wherein the at least one other field expressesthe maximum TOD error as an exponent.
 16. The first STA of claim 13,wherein the FTM message further comprises a time of arrival (TOA) fieldand at least one other field expressing a maximum TOA error in five bitsor less, the at least one other field being capable of expressing themaximum TOA error as large as 1.0 msec.
 17. The first STA of claim 16,wherein the at least one other field being capable of expressing themaximum TOA error as small as 1.0 psec.
 18. The first STA of claim 13,wherein the at least one other field is further capable of expressingthe maximum TOD error as small as 1.0 psec.
 19. A non-transitory storagemedium having computer-readable instructions stored thereon which areexecutable by a process of a first wireless station (STA) to: initiatetransmission of a fine timing measurement (FTM) message through awireless transmitter comprising at least a time of departure (TOD) fieldand at least one other field, the at least one other field expressing amaximum TOD error in five bits or less, the at least one other fieldbeing capable of expressing the maximum TOD error as large as 1.0 msec.20. The non-transitory storage medium of claim 19, wherein the FTMmessage is transmitted in response to receipt of a FTM request messagetransmitted by a second STA.
 21. The non-transitory storage medium ofclaim 19, wherein the at least one other field expresses the maximum TODerror as an exponent.
 22. The non-transitory storage medium of claim 19,wherein the FTM message further comprises a time of arrival (TOA) fieldand at least one other field expressing a maximum TOA error in five bitsor less, the at least one other field being capable of expressing themaximum TOA error as large as 1.0 msec.
 23. The non-transitory storagemedium of claim 22, wherein the at least one other field being capableof expressing the maximum TOA error as small as 1.0 psec.
 24. Thenon-transitory storage medium of claim 19, wherein the at least oneother field is further capable of expressing the maximum TOD error assmall as 1.0 psec.